<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        body {
            margin: 0;
        }

      ul{
        border: 2px solid #666;
        overflow: hidden;
      }
      li{
          float: left;
          width: 100px;
          height: 30px;
          background-color: red;
          list-style: none;
      }
      li:nth-child(even){
          background-color: brown;
      }
    </style>
</head>

<body>
    <ul>
        <li></li>
        <li></li>
        <li></li>
        <li></li>
        <li></li>
    </ul>
</body>

</html>